Process color reproduction is restricted to the use of four colors: cyan, magenta, yellow, and black. A close examination of the color illustrations appearing in most printed material reveals that at most only these four color inks had been used. All variations of tones in the original must be reproduced as faithfully as possible by combinations of these four color inks.
Original art for color reproduction varies widely in quality and nature. It includes oil paintings, water colors, color prints of various kinds, and color transparencies. There are significant differences between these types of art, and it is essential that the designer be thoroughly familiar with the limitations of the reproduction processes as they relate to the different art forms.
Perhaps the most important distinction between types of copy is the difference between reflective copy, e.g., paintings and photographic prints, and transparencies, e.g., Kodachrome and Ektachrome. Reflective copy more nearly resembles the printed page; therefore, faithful reproduction can be more easily attained from reflective copy than from a transparency. In transparencies, several hundred times more light passes through the highlights than passes through the shaded areas. A transparency will always have more detail and brilliance than reflective copy.